A predicted niche shift corresponds with increased thermal resistance in an invasive mite, Halotydeus destructor

Aim Predicted distributions of invasive species are often not congruent between their realized native and introduced ranges, but the reasons for this are rarely investigated empirically. We tested for niche shift in an invasive species using a simple framework combining environmental niche models (ENMs) and niche-limiting thermal tolerance traits. Location Australia and South Africa. Methods The red-legged earth mite, Halotydeus destructor, native to South Africa, is a major agricultural pest in Australia and has expanded its range to areas not predictable from its native range in the last 40 years. Revisiting recently constructed ENMs for H. destructor, we select populations in both native and invasive ranges that appear to occupy different niches. We characterize thermal tolerance traits and test for acclimation patterns of cold tolerance of these H. destructor populations to test for niche shifts. Results Australian populations had an increased upper thermal threshold for movement and were able to recover from cold stress more rapidly than South African populations. Australian populations also differed in trait means from the likely source population in South Africa. Acclimation patterns were conserved across ranges for most populations, with 10 degrees C acclimation lowering the onset of and recovery from cold tolerance and 15 degrees C raising them when compared with field-acclimated populations. Main conclusions These results support the prediction, based on ENMs, that H. destructor may have undergone a niche shift by adapting to environmental conditions in Australia. The increase in thermal resistance has implications for how this invasive species will respond to future climate change.